Grounder to F5. He steps on 3rd, forces R2- 1st out, then throws to F2 to get R3 on the tag for a double play. F2 looks up and sees R2 (who's already out) coming into 3rd. F2 makes a bad throw into left field allowing R1 (who was now on 2nd) to go into 3rd and BR goes into 2nd.

R2 actually continued around 3rd and went home, appearing to "score", on the throw into left.

"7.09
It is interference by a batter or a runner when: ...(f) Any batter or runner who has just been put out hinders or impedes any following play being made on a runner. Such runner shall be declared out for the interference of his teammate; If the batter or a runner continues to advance after he has been put out, he shall not by that act alone be considered as confusing, hindering or impeding the fielders."